U.S. Pat. No. 4,657,229 discloses a rolling-lope air spring which includes essentially a sleeve-shaped rolling-lobe flexible member and a roll-off piston. The air spring has at least one clamp assembly for the pressure-tight attachment of the flexible member to the cover and/or to the roll-off piston of the air spring. The clamp assembly comprises at least one connecting part and a clamp ring. The sleeve-shaped rolling-lobe flexible member is made of elastomeric material, and is without a core and has no end beads. The flexible member also has a reinforcement layer.
The sleeve-shaped rolling-lobe springs, which are filled with a compressible or incompressible medium, and especially sleeve-shaped rolling-lobe flexible member air springs, are preferably used in motor vehicles for suspending the chassis thereof against the unevenness of a roadway. Increasingly, sleeve-shaped rolling-lobe flexible member air springs are also coming into use for suspending driver seats, driver housings and industrial mountings.
Usually, the ends of the sleeve-shaped bodies, which are simply configured without end beads, are attached with the aid of metal clamp rings, on the one hand, at the air spring cover and, on the other hand, at the roll-off piston.
According to the state of the art shown in German patent publication 3,246,962 and U.S. Pat. No. 4,657,229, the attachment regions of air spring cover and roll-off piston are configured with recessed or drawn-in attachment surfaces for the purpose of simplifying assembly. At least an axial part section of the drawn-in attachment surface of the roll-off piston provided with peripherally-extending ribs preferably having a triangular cross section.
With the teaching of U.S. Pat. No. 4,657,229, the exclusive friction-tight attachment disclosed in German patent publication 3,246,962 is supplemented and strengthened by a form-tight connection so that the rolling-lobe flexible members are fixedly attached with greater reliability against any disadvantageous axial displacement.
U.S. Pat. No. 5,460,354 discloses attachment means for a sleeve made of elastomeric material. This attachment means includes a clamp ring having a convex rise which corresponds to a connecting part having a concave recess. The sleeve made of elastomeric material is clamped between the clamp ring and the connecting part for the purpose of a pressure-tight attachment so that the elastomeric material is pressed laterally outwardly. In order to achieve a pressure-tight connection, the elastomeric material must be compressed to approximately 50% of its original material thickness. Since the elastomeric material is practically incompressible, there results theoretically an elongation of the clamping region by 100%. Since the flexible sleeve is intended to contain reinforcement layers of cord, this can only mean that either the cord layer is likewise expandable as the elastomeric material or not. In the last case, a 50% thickness reduction leads to a separation of the elastomeric material from the reinforcement layer. Reinforcement layers having a like expandability as the elastomeric material are not suitable for use in air spring rolling-lobe flexible members.
It is an object of the invention to improve the pull-out strength without damage to the material.
The rolling-lobe spring of the invention includes: a first connecting part; a second connecting part; a sleeve-like, rolling-lobe flexible member arranged between the parts; the flexible member being made of elastomeric material and having a reinforcement layer contained therein; the flexible member having first and second end portions attached to the first and second connecting parts, respectively, and the end portions being devoid of beads and cores; a clamp unit including one of the connecting parts and a clamp ring; the one connecting part having a drawn-in peripherally-extending attachment surface and at least one peripherally-extending raised portion disposed on the attachment surface; the clamp ring having a peripherally-extending recess formed therein and the clamp ring being disposed relative to the attachment surface so that the attachment surface and the clamp ring conjointly define an interface clamping region with the recess facing toward the attachment surface; one of the end portions of the flexible members being disposed in the interface clamping region and being clamped pressure tight between the clamp ring and the stop surface; and, at least one of the raised portion and the recess having a rectangular cross section so as to cause the reinforcement layer to be reorientated when the clamp ring is clamped tightly against the attachment surface with the one end portion being clamped form tightly therebetween.
The connecting parts, which are assigned to the upper and lower end sections of the sleeve-shaped rolling-lobe flexible member, are provided with peripherally-extending raised portions of rectangular cross section in an axial subregion of the drawn-in clamping region. A peripherally-extending recess is provided in the corresponding clamp ring.
In this way, a reorientation of the sleeve-shaped rolling-lobe flexible member including its reinforcement layer is realized. With this reorientation, the sleeve-shaped rolling-lobe flexible member is neither squeezed nor expanded. For this reason, there is not the danger of a separation of the rolling-lobe flexible member material from the reinforcement layer which, for example, can be in the form of reinforcing cords. Damage is in no way to be feared.
Even though the rolling-lobe flexible member is only slightly clamped for the end attachment, but is not squeezed, it has been shown against all expectations that the attachment is also well suited for higher pressures. The following specific dimensions have been shown to be preferred dimensions: the clamp ring has a width of approximately 3 mm; the flexible member has a thickness (b); the clamp ring has a height of approximately 3.5(b); the recess of the clamp ring is at a first distance of 3.5(b) from one end of the clamp ring and a second distance of 0.5(b) from the other end of the clamp ring; and, the recess has a depth of approximately (0.5)(b). The raised portion has a radial height of approximately 0.5(b); the raised portion has a width of approximately 1.5(b); and, the raised portion is at a distance of approximately 3.5(b) to the end of the attachment surface.
With the introduction of a support bell, which encloses the sleeve-shaped rolling-lobe flexible member, the tensile strength of the end attachments of the flexible member is further improved.